Coronavirus mainly spreads from person to person through the air. Anytime someone talks, sings or even breathes, they spread little droplets of liquid called respiratory droplets and even smaller droplets called aerosols. If the person has COVID-19, then these droplets will contain the virus, and if someone else breathes them in they could become infected.
Face masks help stop the spread of COVID-19 in two ways. First, they disrupt the flow of air from your mouth and nose. If you’re infected with COVID-19, but wear a mask, your virus-containing respiratory droplets won’t spread as far.
Second, some face masks can also protect you from catching the virus. These masks filter the air you’re breathing in, stopping virus-containing droplets before you inhale them. Not all face masks are good at this, however. Thin fabric face masks, especially ones that don’t fit securely, aren’t very effective at filtering the virus out. In contrast, properly-fitting, high-grade masks such as KN/N-95 or FFP-2/3 masks can be highly effective at stopping the virus.
If high-grade masks aren’t available, the filtering capacity of fabric masks can be increased by layering multiple masks together (wearing a fabric mask over a surgical/medical mask). The additional layers of fabric help stop the virus, when you’re inhaling and exhaling. It’s not necessary to layer a cloth mask over a high-grade mask, as these are already very good at filtering out the virus.
It’s also not recommended to layer more than two fabric masks, as this could make it more difficult to maintain proper fit and placement of the masks. For masks to work best, they need to seal around your face, so that the air you’re breathing is filtered by the mask. High-grade masks are designed to form a good seal. If you’re wearing fabric masks, however, your protection can be increased by knotting the ear loops to minimise any gaps and ensure a closer fit.
Regardless of which mask you wear, they can become contaminated when worn. So, ensure that you wash your hands before and after taking off your mask, and only touch the ear-loops when removing.
Either discard your mask (if disposable) or wash your fabric mask using soap and warm water or using a washing machine. Masks can also be left in a safe place for three days to decontaminate before wearing again. However, high-grade masks will have specific guidance that needs to be followed.
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Jeremy Rossman is a Senior Lecturer in Virology and President of Research-Aid Networks, University of Kent. His research focuses on the process of infectious disease outbreaks, and he has contributed to studies published in journals including PLoS Pathogens, Bioinformatics and Cell.